The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Archive - California Upwelling

October 08, 2017

Each Sunday we present a notable item from our archives. This EPOD was originally published October 16, 2002.

The above color-coded SeaWiFS satellite image, taken on October 6, 2002, shows upwelling off the California coast. When constant winds blow southward along the west coast of the US, the surface layer of the ocean can be forced away from the coast as a result of the effects of the Earth's rotation and surface friction. As the surface water is pushed offshore, cold, nutrient-rich water upwells from below to replace it. This upwelling facilitates the growth of marine phytoplankton, which is important in nourishing the animal and plant life found along the northern and central California coast. Sensors such as SeaWiFS can detect the effects of this upwelling-related productivity because the chlorophyll-bearing phytoplankton reflects predominantly green light back into space as opposed to the water itself that predominantly reflects blue wavelengths back to space. The upwelling region is color-coded to show chlorophyll concentrations - highest concentrations are shown in red and lowest concentrations are shown in blue. Land and cloud portions of the image are presented in quasi-natural color. [Revised September 2017]